Detecting circuits



v Sept. '22, 1925. v 1,554,266

L. ESPENSCH I ED DETECTING CIRCUITS Filed July 1, 1920 Patented Sept. 22, 1925.

UNITED STATES PATENT GFFlCE.

LLOYD WPENSCHIED, F QUEENS, NEW YORK, AS-SIGNGR TO AMERICE MN TELEIHDIZ'E AND TELEGRAYH COMPANY, A CORPORATION Q3 NEW" YORK.

DETECTING CIRGUITS.

Application filed July 1, i920. Serial No..393,352.

To all whom 2'5 may concern:

Be it. known that. I, Lnorn Esrnnsonmn, residing at Queens, in the county of Queens and State of New York, have invented cer- 5 tain Improvements in Detecting Circuit-s, of

which the following is a specification.

This invention relates toremeiw'ng;- apparatus and, more gmrticulnrly, to receiving apparatus to he used in connection with a 0 signaling system. in which high frequency currents are employed for the transmission of telegraph signals. Heretofore, in the transmission of tele graph signals, by means of carrier currents, whether transmitted over Wires or through the other it has been customary to translate carrier currents at the receiving; station into low frequency signals by means of a detecting apparatus, such as a vacuum tube detector. Since detectors of this character operate by changing" the amplitude oi a direct current, it has heretofore been necessary to use a neutral relay in the output circuit of the detector, as the receiving instrument. Oneof the objects of this invention is to provide a, detector circuit in which a polarized relay may be used for receiving, the signals, although other and further objects of the invention will more fully appear hereinafter.

The invention may now be understood from the following description, when read in connection with the accompanying drawing, Figure 1 of which is a circuit diagram of a detector circuit embodying the prin ciples of thefinvention and Figs. 2 and .3 ol which are curves. illustrating the operation of the receiving apparatus.

Referring to Fig. l. D designates a vucuum tuho detector ol, woll-lmmvn typo. mun

prising afihunent l, a plule 2. and a controlling electrode or grid 3. The input vii cuit of the detcctor is connected between the filament l and the grid 3 and includes the secondary of a transformer 4 and n source of potential 5.

The output circuit of the detector is connected between the filament land the plate 2 and includes the usual plate battery B and one winding 6, of a polarized relay R. The

other winding 7 of the polarized relay is connected in a parallel circuit with the huttery B through a variable resistance 8,

whereby the current flowing through the winding 7 may be regulated. A condenser 9 is shunted across the output circuit. as shown, to term it path of low impedance for rier currents modulated inaccordance with telegraph signals are impressed upon the grid circuit, changes in the grid potential are produced, sothntpulses of direct current flow through the winding 6 of the polarized relay, said pulses corresponding to the signals, in accordance with which the carrier currents were modulated.

It is Well-know that when a. carrier current of a givcnfrequency is modulated by a telegraphic signaling current, such is indicated by the: curve 10 of Fig. 2-, the re snltantmoduluted current may be resolved into a number of components, including an unn'iodulat-ed component of the carrier frequency, a component having a frequency equal to the carrier frequency plus the dot frequency of the signal and another component having a. frequency equal to the carrier frequency minus the (lot frequoi-icy of the signal. Since the signal pulse i'self not of simple sine form. but assumes the form of. an approximately square topped ware. it may he resolved into a sine wave of (lot l'rcqilcncy, upon which are superposed a plurality of WEUOS who e ircxpwucics are various harmonics of the dot =lre(picuc v. tousm ucnt-ly. in addition to the fl'CtlllklllllS uhore rcl'orrcd to. as rom nmouls of the modulated carrier. other frequencies uppcur, lt)l'llfil' ()ll(llll to lhc sums and dillcrcnrrs oi the carrier i'requcucyulul the vuriuuS harmonics of the (lot- Frequency.

When the composite were made up of these various frequencies is impressed upon the grid circuit of the detector D. a reaction takes place between the various component frequencies similar to that taking place during modulation. in other words, frequencies corresponding to the component frequencies of the modulated carrier, together with frequencies corresponding to the sums and differences of these components, appear in the output circuit of the detector.

llO 

